The 10.6.4 Update is recommended for all users running Mac OS X Snow Leopard. It includes Safari 5 and general operating system fixes that enhance the stability, compatibility, and security of your Mac, including fixes that:

resolve an issue that causes the keyboard or trackpad to become unresponsiveresolve an issue that may prevent some Adobe Creative Suite 3 applications from openingaddress issues copying, renaming, or deleting files on SMB file serversimprove reliability of VPN connectionsresolve a playback issue in DVD Player when using Good Quality deinterlacingresolve an issue editing photos with iPhoto or Aperture in full screen viewimprove compatibility with some braille displays